The string is not a valid xpath expression

Hello, 
I'm using a web extension to record my activities through a web page, but whenever put my mouse over a dom element, I get this dom exception : 
DOMException: Failed to execute 'evaluate' on 'Document': The string '//input[@name=btnK and @value=Search]' is not a valid XPath expression.
Is there a way to solve it ? I just started using sideex trying to record my activities on a web page.